This invention relates to offset printing, and in particular to an adjusting mechanism for shifting, for example, a plate cylinder back and forth along its axis of rotation.
Typical multicolor offset presses have at least a pair of plate cylinders simultaneously engageable with a single blanket cylinder. In such a multicolor press, each of the plate cylinders transfers a single-color image to the blanket cylinder. The plate cylinder images are simultaneously transferred to and superimposed on the blanket cylinder, which then transfers the combined images to paper. To ensure proper superposition or registry between the separate images of the plate cylinders on the blanket cylinder, at least one plate cylinder is adjustably movable along its axis of rotation to permit correction of registry errors between the printing plates on the plate cylinders during the press set-up procedures. This adjustment must be made with precision and maintained during press operation. Furthermore, it is desirable to make this adjustment while the press is in operation so that it can be quickly checked in a minimum length of time and a minimum number of wasted copies.